Add option to split the final command inside the CM docker file

[arjunsuresh]

Currently we add the cm run cmd as the final command inside the dockerfile. This means the corresponding CM script and its dependent CM scripts are all executed without docker cache. It is fine if there are no errors but if there is any error, the entire sequence of commands are re-executed. Since we already have an option to generate dependent CM commands for a CM script, it'll be good to add them to the dockerfile when user provides a command line option --docker_split_cm_run_cmd=yes and this way we can make use of docker cache.

This option is useful only when docker_cache=yes.